Cittern

The Cittern used by today's folk-bands has its ancestors in the renaissance Citterns and the English Guitar, but it is now more closely related to the flat-back Bouzouki - the main difference being that the Cittern has 10 strings in 5 courses, a slightly shorter neck and often a rather larger body. There doesn't seem to be a standard tuning, ADADA, ADGAD, or DGDAD, are in common use.